Molds



I. J. LUBALIN April 18, 1961 MOLDS 2 Sheets-Sheet 1 Filed Aug. 9, 1957 FIG. 3

22 FIG. 7

FIG. 4

INVENTOR.

IRWIN J. LUBALIN BY i541 W ATTORNEYS FIG. 5

I April 1961 I. J. LUBALlN 2,979,790

MOLDS Filed Aug. 9, 1957 2 Sheets-Sheet 2 INVENTOR. IRWIN J. LUBALIN [WWW ATTORNEYS Patented Apr. 18, 1961 2,979,790 MOLDS Irwin J. Lubalin, Rockville Centre, N.Y., assignor to Shaw Process Development Corporation, Port Washington, N.Y., a corporation of New York Filed Ang. 9, 1957, Ser. No. 677,262'

' 3 Claims. (c1. 22-129 Molds made from slurries aforesaid which rapidly gel without compacting, i.e., with the gelling being allowed to proceed with a minimum of disturbance, are described in the patent of Noel Shaw, No. 2,795,022. The art is now familiar with the manufacture of such molds. As is known, the gelled mass embodies; volatiles, such as alcohol or other volatiles, as components of the binder. It also evolves volatiles resulting from hydrolysis of the alkyl silicate. When the silicate is ethyl silicate, the alcohol evolved is ethanol.

In carrying out the manufacture of such molds, the gelled mass, that is the mold form, is separated from the pattern and immediately is placed on a suitable support and the volatili'zing alcohol and/ or alcohol plus other volatile solvents, if present, ignited. The high temperature thus generated by the burning of the volatiles efiectuates a freezing of the external mold dimensions. The internal mold structure of the finished mold is characterized by porosity and microcracks. The art recognizes the advantages thereof.

As has been mentioned, the rapid volatilization of the volatiles from the gelled slurry results, if the mold is not immediately ignited or fired, in a shrinking of the mold due to the evaporation of the volatiles. It is necessary, therefore, in order to avoid such shrinking, rapidly to separate the mold form from the pattern and immediately to ignite or fire it after separation from the pattern.

It has now been found that this precaution need not be,

observed if the mold is treated in such wise as to inhibit or markedly restrict the evaporation of the volatiles.

Accordingly, it is among the principal objects of this invention to provide a means for treating a mold of the class described, which is now referred to in the art as a Shaw Process Mold, in such wise as to prevent or very substantially retard the evaporation of volatiles evolving therefrom.

In its fundamental aspects this principal object is achieved by painting or coating a Shaw Process Mold as its surfaces are exposed with a solution of a wax, the solvent of which is quite volatile. In consequence of such coating or painting, the wax, upon volatilization of its solvent vehicle, is left as a deposit on the surface of the mold in a continuous film. This film of wax constitutes a barrier which effectively seals in the volatiles.

In consequence of such coating of the mold form, evaporation of the volatiles is prevented or retarded during the time involved in separating the mold form from the pattern. By this technique the mold form may be very carefully separated from the pattern with consequent preservation of the finest details as a result of the prevention of distortion and shrinking before it is subjected to ignition,

By means of'the instant procedure it is possible, in manufacturing molds for use in casting of three-dimensional objects, to use the green mold half as a base or a support for the pattern in preparing the second half of the mold and thus 'to obtain reduction of the parting'line to a minimum, accurate mating of the mold halves and thereby to achieve perfect reproduction of the pattern.

This new procedure provides a marked advantage over the previous method of producing such halves, wherein the first half had to be ignited immediately upon separation from the pattern, and then, after the completion of the ignition, it was allowed to cool before it could be used in the preparation of the second half. By this new technique of this invention, both halves are true, and make possible the achievement of the closest tolerances known, for matching refractory mold pieces.

Suitable sealants for the purpose described are solutions of waxes such as beeswax, parafiin wax, dental waxes based on blendings of beeswax'and paraflin wax, microcrystalline waxes, etc. Suitable solvents for such waxes are carbon tetrachloride, mineral spirits, gasoline, benzene, and even kerosene, etc. When solvents are used in which the waxes enter slowly into solution at normal or room temperatures, .it has been found that solution thereof is accelerated if the solvent be slightly heated.

A fuller understanding of the invention will become apparent from the following examples taken in connection with the accompanying drawings, which show the various stages in the preparation of the mold forms from the pouring of the slurry up to the time they are ready for ignition.

Example 1 The various stages of preparing a one-piece mold for use in making a casting are illustrated in Figures 1-7.

A pattern, schematically illustrated by the object 10, is placed in a mold box having a bottom 14 and removable walls 16. Then a slurry 18 of comminuted refractory binder and a suitable gelling accelerator, such as the slurry of Shaw Patent No. 2,795,022 or Prange Patent No. 1,909,008, is poured over 10. As taught in the Shaw patent, theslurry is not compacted. When the slurry 18 gels, the top surface 20 thereof is coated, as by brushing or by any other suitable means, with the sealant, a solution of beeswax in carbon tetrachloride gms. of the wax per liter of the solvent). The solvent evaporates, leaving a thin film 22 of the wax. Then the walls 16 are removed, as shown in Figure 4, and the sides 24 of the mold form are similarly coated with the aforesaid wax solution, which leaves films 26 of wax, as shown in Figure 5. Then the mold form, now coated on five sides with the wax film, is carefully separated from the pattern (see Figure 6), and the remaining unwaxed surface 28 is similarly coated with the aforesaid sealant solution to form the wax film 30. The mold form is then ignited, as described in the Shaw patent aforesaid.

Example 2 The various stages of preparing a mold form of two mating halves for use in making castings are illustrated in Figures 8-21.

A mold box 50 is partially filled with clay 52 into which is set a pattern, schematically illustrated by the object 54, as shown in Figure 8. A keying may be provided, as at 56. The mold box is then filled with plaster 58, following which the plaster, when set, is removed. The plaster is then set in the mold box 60 and the pattern 54 positioned therein, as shown in Fig. 11. Following this step, the mold box is then filled with a slurry 62 of comminuted refractory, binder and gelling agent as used in Example 1, as shown in Fig. 12. A

solutionleaving the film 74.

pour hole for use in casting metal may be provided therein by suitable means, as at 64. The top surface 66 is coated with the wax solution of Example 1. Then the walls 68 of the mold box are removed, in manner akin-to the removal of the walls of the mold box as described in Example 1, and the side walls70 of the gelled mold form 62 are then coated with the sealing solution as described in Example has shown in .Fig. 14 The thus wax-coated mold form is separated from the pattern and the unwaxed side 72 coated with the wax After inverting the thus completely wax-coated mold form, it is set in a mold box and the pattern positioned thereinQas shown in Fig. 16. The mold box is then filled with the slurry,

as aforesaid, as shown at 76 in Fig. 17. When the slurry gels, the top surface 78 thereof is coated with the Wax solution, as shown in Fig. 18. Then the walls of the mold box are removed, as shown in Fig. 19, and the sides 80 thereof are coated with the aforesaid wax solution. The mold half 76 ,is then separated from the lower mating half 62 and the pattern 54; and the unwaxed side 84 is then coated with the wax solution at 86. The two wax-coated halves 62 and 76 of the full mold, as shown in Fig. 21, are then ready for ignition.

Example 3 Example 4 A mold form of mating halves is prepared in accordance 'with the general procedure described in Example 2 except that the sealant solution is that used in Example 3.

Example 5 A mold form is prepared in accordance with the gen eral procedure described in Example 1 except that the V sealant solution is that of beeswax'dissolved in gasoline,

- the concentration of the wax in the solution being about percent.

Example 6 A mold form of mating halves is prepared in accordance with the general procedure described in Example 2 except that the sealant solution is the wax solution of Example 5.

The wax content of the sealant solutions may range from about 5 percent to about 40 percent. .Concentrations of the wax in the amount of from about 10 percent to percent are preferred, however, in that they allow for greater fluidity of the Wax solution.

It will be understood that the foregoing description of the invention and the examples set forth are merely illustrative'of the principles thereof. Accordingly, the appended claims are to be construed as defining the invention within the full spirit and scope thereof.

I claim: V

l. A mold form comprising an uncompacted gelled slurry comprising comminutedre'fractory and an alkyl silicate binder containing a volatile material, the entire external surface of the said mold form having thereon a film of wax, whereby the evaporation of volatile materials contained within the mold form is retarded prior to the ignition thereof.

2. A mold form comprising an uncompacted gelled slurry comprising comminuted refractory and an ethyl silicate binder containing a volatile material, the entire external surface of the said mold form having thereon a film of wax, whereby the evaporation of volatile materials contained within the mold form is retarded prior to the ignition thereof.

3.'A mold form comprising an uncompacted gelled slurry comprising comminuted refractory and an ethyl silicate-binder containing a volatile material, the entire 7 external surface of the said mold form having thereon a film of beeswax whereby the evaporation of volatile materials contained within the moldform is retarded prior to the ignition thereof.

References Cited 'in the file of this patent UNITED STATES PATENTS 224,295 Lamb l Feb510, 1880 419,779 "Kaller Jan. 1,1890 697,972 Beabrook Apr. 22, 1902 1,292,964- Ruddell' Jan. 28, 1919 2,045,913 Hoy June 30,1936 2,056,048 Gregory Sept. 29, 1936 2,388,299 Thielemann Nov. '6, 1945 2,480,896; Bean Sept. 6, 1949 2,795,022 Shaw June '11, 1957 

1. A MOLD FORM COMPRISING AN UNCOMPACTED GELLED SLURRY COMPRISING COMMINUTED REFRACTORY AND AN ALKYL SILICATE BINDER CONTAINING A VOLATILE MATERIAL, THE ENTIRE EXTERNAL SURFACE OF THE SAID MOLD FORM HAVING THEREON A FILM OF WAX, WHEREBY THE EVAPORATION OF VOLATILE MATERIALS CONTAINED WITHIN THE MOLD FORM IS RETARDED PRIOR TO THE IGNITION THEREOF. 